Frequency of C9orf72, GRN, and MAPT pathogenic variants in patients recruited at the Belgrade Memory Center.

Most of the heritability in frontotemporal dementia (FTD) is accounted for by autosomal dominant hexanucleotide expansion in the chromosome 9 open reading frame 72 (C9orf72), pathogenic/likely pathogenic variants in progranulin (GRN), and microtubule-associated protein tau (MAPT) genes. Until now, there has been no systematic analysis of these genes in the Serbian population. Herein, we assessed the frequency of the C9orf72 expansion, pathogenic/likely pathogenic variants in GRN and MAPT in a well-characterized group of 472 subjects (FTD, Alzheimer's disease - AD, mild cognitive impairment - MCI, and unspecified dementia - UnD), recruited in the Memory Center, Neurology Clinic, University Clinical Center of Serbia. The C9orf72 repeat expansion was detected in 6.98% of FTD cases (13.46% familial; 2.6% sporadic). In the UnD subgroup, C9orf72 repeat expansions were detected in 4.08% (8% familial) individuals. Pathogenic variants in the GRN were found in 2.85% of familial FTD cases. Interestingly, no MAPT pathogenic/likely pathogenic variants were detected, suggesting possible geographical specificity. Our findings highlight the importance of wider implementation of genetic testing in neurological and psychiatric practice managing patients with cognitive-behavioral and motor symptoms.

Brain Connectivity Networks Constructed Using MRI for Predicting Patterns of Atrophy Progression in Parkinson Disease.

Background Whether connectome mapping of structural and functional connectivity across the brain could be used to predict patterns of atrophy progression in patients with mild Parkinson disease (PD) has not been well studied. Purpose To assess the structural and functional connectivity of brain regions in healthy controls and its relationship with the spread of gray matter (GM) atrophy in patients with mild PD. Materials and Methods This prospective study included participants with mild PD and controls recruited from a single center between January 2012 and December 2023. Participants with PD underwent three-dimensional T1-weighted brain MRI, and the extent of regional GM atrophy was determined at baseline and every year for 3 years. The structural and functional brain connectome was constructed using diffusion tensor imaging and resting-state functional MRI in healthy controls. Disease exposure (DE) indexes-indexes of the pathology of each brain region-were defined as a function of the structural or functional connectivity of all the connected regions in the healthy connectome and the severity of atrophy of the connected regions in participants with PD. Partial correlations were tested between structural and functional DE indexes of each GM region at 1- or 2-year follow-up and atrophy progression at 2- or 3-year follow-up. Prediction models of atrophy at 2- or 3-year follow-up were constructed using exhaustive feature selection. Results A total of 86 participants with mild PD (mean age at MRI, 60 years ± 8 [SD]; 48 male) and 60 healthy controls (mean age at MRI, 62 years ± 9; 31 female) were included. DE indexes at 1 and 2 years were correlated with atrophy at 2 and 3 years (r range, 0.22-0.33; P value range, .002-.04). Models including DE indexes predicted GM atrophy accumulation over 3 years in the right caudate nucleus and some frontal, parietal, and temporal brain regions (R2 range, 0.40-0.61; all P < .001). Conclusion The structural and functional organization of the brain connectome plays a role in atrophy progression in the early stages of PD. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Yamada in this issue.

RFC1 and FGF14 Repeat Expansions in Serbian Patients with Cerebellar Ataxia.

BACKGROUND: The newly discovered intronic repeat expansions in the genes encoding replication factor C subunit 1 (RFC1) and fibroblast growth factor 14 (FGF14) frequently cause late-onset cerebellar ataxia. OBJECTIVES: To investigate the presence of RFC1 and FGF14 pathogenic repeat expansions in Serbian patients with adult-onset cerebellar ataxia. METHODS: The study included 167 unrelated patients with sporadic or familial cerebellar ataxia. The RFC1 repeat expansion analysis was performed by duplex PCR and Sanger sequencing, while the FGF14 repeat expansion was tested for by long-range PCR, repeat-primed PCR, and Sanger sequencing. RESULTS: We identified pathogenic repeat expansions in RFC1 in seven patients (7/167; 4.2%) with late-onset sporadic ataxia with neuropathy and chronic cough. Two patients also had bilateral vestibulopathy. Repeat expansions in FGF14 were found in nine unrelated patients (9/167; 5.4%) with ataxia, less than half of whom presented with neuropathy and two-thirds with global brain atrophy. Tremor and episodic features were the most frequent additional characteristics in carriers of uninterrupted FGF14 repeat expansions. Among the 122 sporadic cases, 12 (9.8%) carried an expansion in either RFC1 or FGF14, comparable to 4/45 (8.9%) among the patients with a positive family history. CONCLUSIONS: Pathogenic repeat expansions in RFC1 and FGF14 are relatively frequent causes of adult-onset cerebellar ataxia, especially among sporadic patients, indicating that family history should not be considered when prioritizing ataxia patients for testing of RFC1 or FGF14 repeat expansions.

DYT-THAP1: exploring gene expression in fibroblasts for potential biomarker discovery.

Dystonia due to pathogenic variants in the THAP1 gene (DYT-THAP1) shows variable expressivity and reduced penetrance of ~ 50%. Since THAP1 encodes a transcription factor, modifiers influencing this variability likely operate at the gene expression level. This study aimed to assess the transferability of differentially expressed genes (DEGs) in neuronal cells related to pathogenic variants in the THAP1 gene, which were previously identified by transcriptome analyses. For this, we performed quantitative (qPCR) and Digital PCR (dPCR) in cultured fibroblasts. RNA was extracted from THAP1 manifesting (MMCs) and non-manifesting mutation carriers (NMCs) as well as from healthy controls. The expression profiles of ten of 14 known neuronal DEGs demonstrated differences in fibroblasts between these three groups. This included transcription factors and targets (ATF4, CLN3, EIF2A, RRM1, YY1), genes involved in G protein-coupled receptor signaling (BDKRB2, LPAR1), and a gene linked to apoptosis and DNA replication/repair (CRADD), which all showed higher expression levels in MMCs and NMCs than in controls. Moreover, the analysis of genes linked to neurological disorders (STXBP1, TOR1A) unveiled differences in expression patterns between MMCs and controls. Notably, the genes CUEDC2, DRD4, ECH1, and SIX2 were not statistically significantly differentially expressed in fibroblast cultures. With > 70% of the tested genes being DEGs also in fibroblasts, fibroblasts seem to be a suitable model for DYT-THAP1 research despite some restrictions. Furthermore, at least some of these DEGs may potentially also serve as biomarkers of DYT-THAP1 and influence its penetrance and expressivity.

ANO10-Related Spinocerebellar Ataxia: MDSGene Systematic Literature Review and a Romani Case Series.

BACKGROUND: Biallelic pathogenic variants in the ANO10 gene cause autosomal recessive progressive ataxia (ATX-ANO10). METHODS: Following the MDSGene protocol, we systematically investigated genotype-phenotype relationships in ATX-ANO10 based on the clinical and genetic data from 82 published and 12 newly identified patients. RESULTS: Most patients (>80%) had loss-of-function (LOF) variants. The most common variant was c.1150_1151del, found in all 29 patients of Romani ancestry, who had a 14-year earlier mean age at onset than patients homozygous for other LOF variants. We identified previously undescribed clinical features of ATX-ANO10 (e.g., facial muscle involvement and strabismus) suggesting the involvement of brainstem pathology, and we propose a diagnostic algorithm that may aid clinical ATX-ANO10 diagnosis. CONCLUSIONS: The early disease onset in patients with c.1150_1151del may indicate the existence of genetic/environmental disease-modifying factors in the Romani population. Our findings will inform patient counseling and may improve our understanding of the disease mechanism. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.